We are using a model of local pulmonary endotoxin administration to study acute inflammatory events in the lung (92-CC-0141). This model provides a means of evaluating mechanisms that are important in regulating the recruitment of cells to an inflamed focus and factors contributing to the resolution of the inflammatory response. Urokinase plasminogen activator (UPA) is an important molecule in the conversion of plasminogen to plasmin, which initiates fibrinolysis. A product of this conversion is angiostatin, a potent angiogenic factor. Receptors for UPA (UPAR) and plasmin are local-ized on migrating leukocytes and cause hydrolysis of the extracellular matrix. In addition UPAR contributes to beta2-integrin dependent adherence and chemotaxis. We are studying the importance of UPA-UPAR in acute lung inflammation by: (1.) Measuring fibrinolytic proteins and their respective receptors and inhibitors in acute phase lavage fluid. (2.) Using an in vitro system of human endothelial-epithelial bilayers grown on a collagen matrix to evaluate the contribution of UPA-UPAR to neu-trophil migration. Cells will be evaluated using flow cytometry, immunohistochemical staining. (3.) Early gene expression will be evaluated using RNAase protection assays from samples obtained in vivo and from the in vitro system